Attempt to produce large numbers of active suppressor T-cells for both mouse and human cell-mediated immune responses. Isolate soluble suppressor products of these supp essor T-cells and identify and characterize them for cellular immune functions. Attempt to elucidate the mechanism of action and effects of soluble suppressor substances and cells. Determine if T-cells which regulate cell-mediated and humoral immune responses are distinct and separable populations or just diverse effects of a single regulatory T-cell population. Test suppressor products in mouse model for in vitro suppression of cell-mediated immunity and effect on human lymphocytes in vitro (MLC). Determine if effects of suppresso T-cells or their soluble products are either antigen or species specific or both.